Conventional multimedia service technology has been focused on proposing techniques for minimizing the delay attributable to data transmission and for pursuing excellence in terms of performance. Further, the conventional multimedia service technology depends on techniques that provide encapsulation and integrity by encrypting all data to provide data security. However, video data has the advantage of, because only a part of data fundamentally required to reconstruct video is selectively encrypted unlike typical non-multimedia data (for example, text data), being able to provide the same security as is obtained when all of the data is encrypted. That is, such selective encryption allow problems to be avoided, namely the problem of the occurrence of an additional overhead due to having to encrypt all the data and there being a delay in playing attributable to the decryption of video upon decoding the video.
However, there are problems in that the exact evaluation of the performance overhead based on selective encryption is insufficient at present, and contents related to the configuration of security are not treated as principal elements of performance.
In addition, the security provided by a conventional multimedia distribution service is provided to the extent of checking only the rights to use the content using a simple access control technique and of determining whether to provide the content. For example, there is a serious disadvantage in that since content has been distributed with the same security applied to a single piece of content, the distribution of content can be conducted without permission by illegally accessing the content once the security vulnerabilities of the relevant content has become known by the world at large.
However, as Scalable Video Coding (SVC), which is a video compression standard that is an extended version of International Telecommunications Union—Telecommunication Standardization Sector (ITU-T) H.264/Advanced Video Coding (AVC) standard, has recently appeared, multi-layered coding transport technology has been actualized. Accordingly, the structure of content can be variably reorganized in conformity with service requirements by performing encoding a single time. For example, depending on requirements such as the performance of a specific reception terminal, the bandwidth situation of a transmission network, or the degree of subscription to a video streaming service, video data of a quality suitable to those requirements can be dynamically configured and provided in terms of three kinds of scalability (resolution, Frames per Second (FPS), Signal-to-Noise ratio (SNR)).
Content that can be distributed in various units depending on the service situation using video compression technology such as the SVC standard is designated as scalable content, and a basic unit constituting each piece of scalable content is designated as a scalable unit.
Accordingly, there has been a heightened need to provide differentiated security in terms of performance by providing content on a scalable unit basis rather than providing content on a piece-of-content basis any longer. The provision of individual security denotes a scheme in which different security techniques need to be operated for respective scalable units. Therefore, there is the probability of an increase in complexity due to the distribution of scalable content that has been encoded using an SVC standard. Therefore, when any security technique is given, accurately evaluating the influence of the security technique exerted in terms of performance and security of the entire service is an urgent requirement.
In addition, existing research into the protection of scalable content has generally revealed a tendency to regard a visual distortion index such as visual degradation as important on the basis of the results of experiments conducted on individual videos. However, in order to provide adaptive optimal security for content, relationships between various indices, such as encryption speed, protection strength, device capacity, required streaming video quality, visual distortion, network cost and redistribution cost, need to be considered together within the scope of a security policy.